Cellulose nanofibers which have been recently developed are nanofiller composed of plant-derived natural raw materials and attract attention as low-specific-gravity and high-strength composite materials for resins.
However, in order to fibrillate cellulose having many hydroxyl groups up to a nano-level, in view of the current technology, it is necessary to fibrillate cellulose in water or fibrillate a mixture of a resin with a large amount of water, and thus cellulose nanofibers after fibrillation contain a large amount of water (refer to Patent Literature 1). In order to produce composites of the hydrated fibrillated cellulose nanofibers with various resins, a step of dehydrating the produced cellulose nanofibers is required. In addition, cellulose easily forms intermolecular hydrogen bonds, and thus re-aggregation takes place in the step of dehydrating cellulose nanofibers, thereby degrading dispersion in a resin.
In order to resolve the problems, a technique of fibrillating cellulose in an organic solvent, not in water, to produce cellulose nanofibers is reported (refer to Patent Literature 2). This technique decreases drying cost because water is not required, but in order to form a composite with a resin, a step of dispersing cellulose in an organic solvent and then removing the organic solvent after fibrillation is required, and a complicated process for producing nanofibers is not yet improved.
That is, there is demand for establishing a technique capable of forming composites of cellulose nanofibers with various resins by a low-cost simple process.